This study prospectively defined the range of left ventricular mass and volume/mass ratio determined by two-dimensional echocardiography in 84 normal adults. A modified Simpson's rule algorithm was used to calculate ventricular volumes from orthogonal two and four chamber apical views. An algorithm based on a model of the left ventricle as a truncated ellipsoid was used to calculate ventricular mass. Like left ventricular volumes, left ventricular mass values were larger in normal men than in women (mean 148 versus 108 g, p less than 0.001) and remained larger after correction for body surface area. Volume/mass ratios, however, were constant at end-diastole (0.80) and end-systole (0.26). The influence of age and heart rate on all variables in this normal group was minimal, and no correction for these variables was necessary. The definition of normal mass, volume and volume/mass ratios by two-dimensional echocardiography will facilitate the noninvasive, quantitative diagnosis of left ventricular hypertrophy and help clarify the relation between hypertrophy and systolic wall stress.